1. Field of the Invention
The present invention relates generally to cutting apparatus, and, more particularly, to a shield cup protector apparatus for protecting the shield cup of a plasma arc torch.
2. Description of the Prior Art.
Plasma arc torches are utilized with great frequency for the performance of various metal cutting and welding operations. The plasma arc torch generates a high-temperature discharge which allows fast and uniform cutting and/or welding of the metal.
In some instances, the torch is portable and may be hand-held. In other instances, the torch comprises a portion of a machine. In each design, though, the torch is comprised of a torch body which supports an electrode, from which the plasma arc discharge occurs. Electrical power and an ionizable gas are supplied to the torch body, where the gas is ionized, thereby causing the plasma arc across the electrode. In most instances, a ceramic shield cup surrounds torch tip to provide a passage way for the secondary or shield gas.
The shield cup of a plasma arc torch is comprised of a ceramic material because of the heat-resistant quality thereof. However, brittleness is also a quality of ceramic materials.
During operation of the plasma arc torch in various metalworking applications, a constant distance, the stand-off distance, must be maintained between the torch tip (i.e., the torch electrode) and the metal workpiece. This constant separation distance is difficult to maintain, and, in some instances, the torch operator is unable to maintain the separation distance, and allows the ceramic shield cup to contact the workpiece. Because of the brittleness of the ceramic shield cup, the impact of the workpiece may cause the shield cup to break. Such breakage of the shield cup necessitates replacing the shield cup prior to further use of the plasma arc torch.
Several devices are available to alleviate this problem. One such device is sold by Thermal Dynamics Corp. and comprises a carriage with two wheels attached to the torch by a clamp. This device primarily maintains a stand-off distance, and offers little protection to the shield cup for preventing its breakage. Thermal Dynamics also markets a "Crown Shield Cup" which similarly maintains a stand-off distance, but is comprised of a ceramic material susceptible to breakage.
It is therefore the object of the present invention to provide an apparatus to prevent damage to the ceramic shield cup of the plasma arc cutting torch.
It is a further object of the present invention to provide a shield cup protector apparatus which maintains a proper stand-off distance between the torch tip and the workpiece while allowing exhaust of slag and gases from the work site.